Electric control system



2 Sheets-Sheet l A. SCHMIDT, JR

ELECTRIC CONTROL SYSTEM Filed Dec. 9, 1936 March 22, 1938.

M ..& w A H mm 1 O wmw e 1 W M March 22, 1938. A SCHMIDT JR 2,112,051

ELECTRIC CONTROL SYSTEM Filed Dec. 9, 1936 2 Sheets-Sheet 2 Inventor: August SChmid-t,JT'I

y wad/ 2 14W His Attorney.

Patented Mar. 22, 1938 UNITED STATES PATENT OFFICE 2,112,051 I ELECTRIC CONTROL SYSTEM of New York Application December 9, 1936, Serial No. 114,986

6Claims.

My invention relates to electric control systems and more particularly to circuits for operating .electric valve means and dynamo-electric machines in parallel.

It has become apparent that there is a decided-need for control circuits suitable for translating systems in which a plurality of different translating devices such as .electric valve means and dynamo-electric machines are intended to operate in parallel. The control circuits, in order to be susceptible of a reasonable range of application, must be simple in construction and arrangement, and must be capable of responding rapidly and precisely to load or supply circuit conditions to effect a predetermined division of load between the electric valve means and the dynamo-electric machine. He'retofore, the above desirable features have not been found in the available control circuits for performing these functions.

It is an object of my invention to provide new and improved electric translating system.

It is another object of my invention to provide a new and improved electric control circuit.

It is a further object of my invention to provide a new and improved control system for operating electric valve apparatus and dynamo electric machines in parallel.

In accordance with the illustrated embodiment of my invention, I provide a new and improved control system for operating electric valve appa ratus and dynamo-electric machines in parallel. More specifically, I provide a system in which an electric valve means and a dynamo-electric ma chine are operated in parallel to transmit energy between a load circuit and a supply circuit. I have chosen to represent my invention as applied to a system including a synchronous converter and an electric valve means connected in par-= allei to transmit energy between an alternating current circuit and a direct current circuit. A control circuit is employed to impress on control members of the electric valve means an alternating voltage the phase of which varies relative to the voltage impressed across the electric valve means conjointly in accordance with the current supplied by the electric valve means and the current supplied by the synchronous converter to maintain a predetermined division of load.

For a better understanding of my invention reference maybe had to the following description taken in connection with the accompanying drawings and its scope will be pointed out in the appended claims. Fig. l of the accompanying drawings diagrammatically illustrates an embodiment of my invention as applied to an eleo trlc translating system in which an electric valve means and a synchronous converter are operated in parallel and Fig. 2 shows certain operating characteristics thereof.

Referring to Fig. 1 of the accompanying drawings, I have diagrammatically shown my invention as applied to an electric translating system including a plurality of diflerent translating devices for transmitting energy between an alternating current circuit 5 and a direct current circult 2. A dynamo-electric machine 3, which for the purpose of explaining my invention is shown as a synchronous rotary converter, is connected to operate in parallel with an electric valve means t including electric valves 5, B and i. Each of the electric valves 5, 6 and l includes an anode il, a cathode c and a control member I and is preferably of the type employing an ionizable medium such as a gas or a vapor. Electric valves Ti, 8 and l are connected to the alternating cur rent circuit i through a transformer it having primary windings i2 and secondary windings i3. Secondary windings it are connected to provide a neutral connection it which is connected to one terminal oi the direct current circuit 2 and to the corresponding terminal of the direct cur rent circuit of the synchronous converter While have diagrammatically shown my inven tion as applied to an electric translating circuit in which the dynamo-electric machine is a synchronous converter, it should be understood that invention in its broader aspects could be applied to electric translating systems generally where it is desired to operate electric valve apparatus and other types of dynamo-electric ma chines parallel.

In order to provide an arrangement for con trolling the electric valve means t to maintain a predetermined division of load between the electric valve means 4 and the synchronous con-= verter 3, I provide a pliuality of control circuits i5, i6 and il including inductive devices i8, i9 and 20 respectively. The circuits l5, l5 and il may be energized from any suitable source oi alternating current correlated in the proper mannor in frequency and phase relative to the voltage of the alternating current circuit i. In the particular arrangement shown in Fig. l, the control circuits i5, i6 and ii are energized from the alternating current circuit l through any conventional phase shifting arrangement such as the rotary phase shifter 2!. The inductive devices i8, I9 and 20 are energized from a three-phase output circuit 22 of the rotary phase shifter 2| and each is energised in accordance with the voltage of a diii'erent phase oi the three-phase alternating current circuit 22. a

The inductive devices l3, l3 and 23 are substantially similar in construction and arrangement, and for the purposes of describing these devices, one of the devices, such as the inductive device II will be considered in particular. The inductive device l3 includes a core member 23 having a saturable path 24 and a member 23 arranged to shunt the saturable portion 24 when the magnetization'oi the path 24 exceeds a predetermined value. The saturable portion or path 24 may be constructed of any suitable material, such as a material which saturates very rapidly for values 01' flux above a predetermined value/ A winding 23 which is energized from one phase of the alternating current circuit 22 serves to impress on the core member 23 an alternating magnetcmotive force. The winding 23 may be energized through a variable resistance 21 which serves to adjust the voltage impressed thereon. To impress on the core member 23 a unidirectional magnetomotive force which varies in magnitude in accordance with an electrical condition of the electric valve means 4, such as the current supplied by the electric valves 3, 3 and I, I provide a control winding 23 which is wound around or inductively associated with the saturable path 24 01' the inductive device i3. A control winding 23, which is oppositely disposed relative to the winding 23, is also inductively associated with the saturable path 24 of the inductive device l3 and serves to impress upon the core member 23 a unidirectional magnetomotive force in opposition to the magnetomotive force oi winding 23 and which varies in magnitude in accordance with an electrical condition such as the current conducted by the synchronous converter 3. A winding 33 is also wound on the saturable path 24 or conductively associated therewith and provides an alternating voltage of peaked wave form, the phase of which varies relative to the voltageimpressed anode 3 and cathode 3 of electric valve 3 conjointly in accordance with the resultant unidirectional magnetomotive force in the core member 23, or in other words varies coniointly in accordance with the division of load between the electric valve means 4 and the rotary converter 3. The winding 33 impresses the voltage of peaked wave form on control member l3 of electric valve 3 through a current limiting resistance 3|. Any suitable source of voltage, such as a battery 32 may be employed to impress on the control members l3 oi electric valves 5, 3 and 1 a negative biasing potential.

. windings 23 of the inductive devices l3, l3 and 23 may be connected in series relation with each other. In the particular arrangement shown, these windings are energized in accordance with the voltage appearing across an adjustable resistance 33 which is connected in series relation with the electric valve means 4. In like manner the control windings 23 of inductive devices i 3, l3 and 23 may be connected in series relation across an adjustable resistance 34 which is connected in series relation with the direct current circuit oi the synchronous converter 3. While for the purposes of explaining my invention I have shown the windings 23 as being energized in accordance with the current or the direct cm'rent circuit oi the synchronous converter 3, it will be understood that I' may employ other suitable means such as a conventional rectifier which energizes the windings 23 in accordance with another electrical condition oi the synchronous converter 3. such as the current in the alternating current circuit oi the converter. Furthermore, it should be understood that the control windings 23 of inductive devices l3, l3 and 23 may also be energized through suitable rectifying devices in accordance with an alternating quantity of the electric valve means 4 or associated circuit.

The operation of the embodiment of my invention diagrammatically shown in Fig. 1, will be explained by considering the electric translating system when the electric valve means 4 and the rotary synchronous converter 3 are operating in parallel relation to transmit energy from the alternating current circuit to the direct current circuit 2. Let it be assumed that it is desired to maintain a predetermined division of load be-\ tween the electric valve means 4 and the synchrcnous converter 3; more specifically, let it be assumed that it is desired to maintain an equal division of load between the electric valve means 4 and the synchronous converter 3. As it is well understood by those skilled in the art, the electric valves 3, 3 and I may be rendered conductive by impressing upon the control members l3 potentials sumciently positive relative to the cathodes during those intervals in which the anodes 3 are positive relative to the cathodes 3. Furthermore, it will be understood that the conductivity of the electric valves 3, 3 and I, or, in other words, the current which these valves conduct will be substantially zero when the alternating voltages impressed upon the control members i3 are in substantial phase opposition to the alternating voltages impressed upon the anodes 3. On the other hand, the conductivity of electric valves 3, 3 and I, and hence the current conducted by these electric valves will be a maximum when there is substantial phase coincidence between the alternating voltages impressed upon the control members l3 and the alternating voltages impressed upon the associated anodes 3. For the purpose of explaining my invention, let it be assumed that the adjustable resistance 33 is adjusted so that the current supplied to the control windings 23 is greater than the current supplied to the control windings 23, and let it be assumed further that the windings 23 and 23 are arranged relative to the instantaneous polarizations 01' the windings 23 so that an increase in the energization of the windings 23, or in other words, an increase in the resultant unidirectional magnetomotive forces will effect a retardation in phase of the alternating voltages induced in windings 33 01' inductive devices l3, l3 and 23 relative to the voltages impressed on the various anodes 3.

The inductive devices l3, l3 and 23 by virtue of the peculiar design oi the core members 23 serve to induce voltages of peaked wave form in the windings 33. Neglecting the eilect oi the unidirectional magnetomotive forces impressed on the core member 23 by control windings 23 and 23, the maximum value 01' the flux threading the saturable path 24 of each 01' the core members 23 will remain substantially constant during each hali cycle of alternating magnetomotive force. In other words, due to the fact that the saturable path 24 becomes saturated, there will be induced in the winding 33 a voltage of peaked wave form at the time when the magnetomotive iorce passes through the zero value. The magnetic path 23 serves to shunt the flux around the saturable path 24 when the path 24 becomes saturated maintaining therein a substantially constant value of flux during each half cycle. The eflect oi the resultant unidirectional magnetomotive force impressed onthe core member 23 by the control windings 28 and 29 is to shift the time at which the resultant magnetomotive force passes through zero and hence to eflect a shift in the phase of the voltage of peaked wave form relative to the voltage impressed on winding 28.

The operating characteristics represented in Fig.2 will be considered in explaining the operation of the embodiment of my invention shown in Fig. 1. In Diagram I of Fig. 2, curves A, B and C represent the three-phase alternating voltages impressed upon electric valves 5, 8 and l, and curve D 0! Diagram II represents the magnetomotive force impressed on core member 23 of inductive device l8. This particular phase position of the magnetomotive force impressed on core member 23 of inductive device I8 is obtained by adjustment of the rotary phase shiiterfl. In Diagram III, the line E represents the negative unidirectional magnetomotive force impressed on the core member 23, or in other words, the position of the line E represents the difl'erence between the magnetomotive force provided by the control winding 28 and the magnetomotive iorce provided by the control winding 29. This partic-= ular relation may be obtained by the adjustment of adjustable resistances 33 and 34, or by the design of the control windings 28 and 29. The curve F represents the resultant magnetomotive force impressed on the core member 23 and is obtained by combining the curve D of Diagram Ii with the line E of Diagram III. It will be noted that the curve F intersects the zero axis at points a and b. When the resultant magnetomotive iforce impressed on the core member 23 passes through zero corresponding to the position of the points a and b, there will be induced in the wind-= ing 30 an alternating voltage of peaked wave form. Curve G of Diagram IV represents this voltage of peaked wave form. It should be understood that the curve G represents only the voltage impressed on control member Ill of electric valve 5 by the inductive device l8, and that corresponding voltages of peaked wave form are impressed on control members in of electric valves 6 and l by inductive devices l9 and 20. These latter voltages, of course, will be displaced in phase rela= tion to the voltage G in accordance with the conventional three-phase system of voltages. The displacement c of the curve G from the zero axis is effected by means of the battery 32. By virtue of the voltage of peaked wave form occurring at point a, the electric valve means 5 will be rendered conductive at this time so that there is impressed upon the load circuit 2 a voltage substantially equal to the corresponding position of the curve A. In like manner the voltages impressed upon control members I 0 of electric valves 6 and 1 will render these valves conductive at times corresponding to the position of lines 0? and e so that there is impressed on the direct current circuit 2 a voltage which may be represented by curve H of Diagram V. Under these conditions it will be assumed that with the electric valve means 4 supplying a voltage as represented by curve H, the division of load between the electric valve means 4 and the rotary converter 3 will be substantially equal.

If it be assumed that for any reason the synchronous converter 3 begins to assume a greater portion of the load than that for which the control circuits l5, l6 and II have been adjusted, the energization of the control windings 29 o! inductive devices II, II and 23 will be increased to eflect a decrease in the resultant unidirectional magnetomotive force impressed upon core members 23 or inductivqdevices I8, I9 and 20. Line .1

0! Diagram VI represents the decreased undirec tional magnetomotive force impressed on the core members of one oi the inductive devices such as inductive device l8, and the curve K represents the resultant magnetomotive force impressed on the core member 23. It will be noted that the resultant magnetomotive force as represented by curve K intersects the zero axis at a point I to effect an advancement in phase of the alternating voltage of peaked wave form induced in winding 30. This alternating voltage is represented by curve M oi Diagram VII. By virtue of this decrease in the resultant magnetomotive force in the core member 23, the phase of the voltage of peaked wave form induced in winding 30 is advanced relative to the voltage impressed across anode 8 and cathode 9 of electric valve 5 by an angle corresponding to the distance between points a and j. Coincidentally with this decrease in magnetomotive force in core member 23 of device 3, the core members 23 of inductive devices l9 and 20 will also experience similar efiects and the alternating voltages impressed on control members it! of electric valves 6 and i will be advanced in phase relative to the respective anode voltages so that the voltages impressed on the direct current circuit 2 by electric valve means i is increased to cause the electric valve means 4 to assume a larger portion of the ioad to effect thereby a reestablishment of. the predetermined equal division of load. VIII represents the voltage impressed on the direct current circuit 2 by the electric valve means 4 under the conditions set forth in Diagrams VI and Conversely, when the electric valve means t assumes a greater portion of the load than that for which the system is adjusted, the increased energiaation oi windings 28 of inductive devices 98, i9 and 2% will increase the resultant unidirectional magnetomotive forces so that the voltages induced in the windings 30 are retarded in phase to reduce the voltage of the electric valve means it. In this wav, after an initial adjustment. the translating system will operate to maintain a predetermined division of load between the electric valve means i and the synchronous converter 3.

Whilefor the, purpose of explaining the operation of my invention I have chosen to describe the operation thereof when the system is cons dered to be transmitting energy from an alternating current circuit to a direct current cir= cult, it is to be understood that my invention may be employed to effect a predetermined division of load between the electric valve means 4- and the synchronous converter 3 when these elements are operating as inverters to transmit energy from a direct current circuit to an alternating current circuit.

While I have shown and described my invention as applied to a particular system of connections and as embodying various devices diagrammatically shown, it will-be obvious to those skilled in that art that changes and modifications may be made without departing from my invention, and I, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

The curve N of Diagram WhatIclaimasnewandde'siretosecureby Letters Patent of the United States. is:

1. In combination, a supply circuit, a load circuit, a plurality of translating devices interposed in parallel relation between said circuits for transmitting energy therebetween and including at least one electric valve means having an anode, a cathode anda control member, and means for efiecting a predetermined distribution of load between said electric valve means and the other oi said translating devices comprising an inductive device for impressing on said control member an alternating voltage variable in phase relative to the voltage impressed across said anode and cathode coniointly in accordance with the current transmitted by said electrical valve means and the current transmitted by the other of said translating devices. 2. In combination, a supply circuit, a load circuit, electric valve means having an anode, a cathode and a control member and a dynamoelectric machine connected to operate in parallel to transmit energy between said circuits, and means for impressing on said control member an alternating voltage variable in phase relative to the voltage impressed across said anode and cathode conjointly in accordance with the load current of said electric valve means and the load current oi said machine to maintain a predetermined division of load between said electric valve means and said machine.

3. In combination, a supply circuit, a load circuit, electric valve means having an anode, a cathode and a control member and a dynamoelectric machine interposed between said circuits and arranged to operate in parallel, and means for electing a predetermined division oi'load between said electric valve means and said machine comprising an inductive device including a core member, a winding for impressing on said core member an alternating magnetomotive force, a control winding tor impressing on said core member a unidirectional magnetomotive force which varies in accordance with an electrical condition of said electric valve means, a second control winding for impressing on said core member a second unidirectional magnetomotive force which opposes said first mentioned magnetomotive force and which varies in accordance with an electrical condition of said machine and a winding responsive to a magnetic condition of said core member for impressing on said control member an alternating voltage variable in phase relative to the voltage impressed across said anode and said cathode.

4. In combination, an alternating current circuit, a direct current circuit, an electric valve means having an anode, a cathode and a control member and a dynamo-electric machine interposed between said circuits and connected to operate in parallel, and means for electing a predetermined division of load between said electric valve means and said dynamo-electric machine comprising an inductive device having a core member, a winding for impressing an alternating magnetomotive force on said core memarraosr ber, a control winding ior impressing on said core member a unidirectional magnetomotive force which varies in magnitude in accordance with an electrical condition of said electric valve means, a second control winding for impressing on said core member a unidirectional magnetomotive iorce in opposition to said first mentioned unidirectional magnetomotive force which varies in magnitude in accordance with an electrical condition of said dynamo-electrical machine and a winding responsive to the resultant fiux in said core member for impressing on said control member an alternating voltage the phase 01' which varies relative to the voltage impressed acrou said anode and said cathode to maintain said predetermined division 01' load.

. 5. In combination, an alternating current circuit, a direct current circuit, an electric valve means having an anode, a cathode and a control member and a synchronous converter connected in parallel relation between said circuits,

and means for controlling said electric valve means to efiect a predetermined division of load between said electric valve means and said synchronous converter comprising an inductive device having a core member, a winding for impressing on said core member an alternating magnetomotive force, a control winding for impressing on said core member a unidirectional magnetomotive force variable in magnitude in accordance with the current of said electric valve means, a second control winding for impressing on said core member a unidirectional magnetomotive force in opposition to said first mentioned magnetomotive force and variable in magnitude in accordance with the current of said synchronous converter and a winding responsive to a magnetic condition of said core member for impressing on said control member an alternating voltage of peaked wave form variable in phase relative to the voltage impressed across said anode and said cathode to maintain said predetermined division of load.

6. In combination, a supply circuit, a load circuit, electric valve means having an anode, a cathode anda control member and a dynamoelectric machine connected to operate in parallel to transmit energy between said circuits. and an inductive device having a core member including a saturable portion and a shunt magnetic path therefor, a winding for impressing an alternating magnetomotive force on said core member, a winding responsive to a magnetic condition of said saturable portion for providing an alternating voltage of peaked wave form and a pair of control windings for impressing opposing unidirectional magnetomotive forces on said core member to control the phase of said alternating voltage relative to the voltage impressed across said anode and said cathode coniointly in accordance with an electrical condition 01 said electric valve means and an electrical condition of said machine to maintain a predetermined division of load therebetween.

AUGUST SCHMIDT, Ja. 

